Removing a string from array MongoDB object

Question

I have objects like in my collection:

{
   "foo": {
       "actions": [
          ...,
          "delete"
       ]
   },
   "bar": {
      "tags": ["links", ...]
   }
}

I want to remove delete value from foo.actions from all objects that contain links value in bar.tags field.

I tried to do a basic update that seems not to work:

db.foo.update({
   "bar.tags": /links/
}, {
   $pull: {
       "foo.actions": "delete"
   }
}, {
   multi: true
});

delete field is not removed since the following request doesn't return 0:

> db.foo.find({"bar.tags": /links/, "foo.actions": /delete/}).count()
786

What's the issue here? Why delete value is not removed?

@JohnnyHK tags is inside of another object. Maybe that makes the difference? — Ionică Bizău
– Ionică Bizău, Commented Sep 8, 2014 at 16:56

Larry Battle · Accepted Answer · 2014-09-08 17:22:11Z

2

It worked for me. Maybe you're not calling the right collection. What you want to do is print the count before and after the update to see if there's a difference.

Example:

db.foo.find({"bar.tags": /links/, "foo.actions": /delete/}).count() // 4
db.foo.update({
   "bar.tags": /links/
}, {
   $pull: {
       "foo.actions": "delete"
   }
}, {
   multi: true
});
db.foo.find({"bar.tags": /links/, "foo.actions": /delete/}).count() // 0

Setup

var createObj = function(){
  var o = {
     "foo": {
         "actions": [
            "ok"
         ]
     },
     "bar": {
        "tags": ["links"]
     }
  }
  if( Math.random() < 0.5 ){
    o.foo.actions.push("delete");
    o.foo.actions.push("delete");
    o.foo.actions.push("delete");
  }
  return o;
};
use test;
db.foo.drop();
for(var i = 0; i < 10; i++){
  db.foo.insert( createObj() );
}

answered Sep 8, 2014 at 17:22

Larry Battle

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3 Comments

Ionică Bizău Over a year ago

It's strange that running db.foo.update({"bar.tags": "links", "foo.actions": "delete"}, {"$pull": {"foo.actions": "delete"}}, {multi: true}) worker perfectly. Anyway, thanks for great answer!

Ionică Bizău Over a year ago

The issue appeared because I was having a field deleteImage in foo.actions. When I was counting foo.actions: /delete/ they were being caught. Can you please update your answer with this information? May be useful for future users.

Larry Battle Over a year ago

You might want to use a string instead of a regular expression next time. Because /delete/ matches any word that contains delete and not just the word delete. /^delete$/ is the same as "delete".

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